It is very important in the field of ophthalmic devices and in particular in the field of contact lenses, that the lens is biocompatible and does not cause damage to the surrounding ocular tissue nor inhibit ocular fluid generation or flow during the time period of contact. In particular, it is critical that a sufficient amount of oxygen is able to reach the cornea while contact lenses are worn, otherwise eye health may become negatively impacted. For example, an inadequate supply of oxygen to the cornea can result in edema or swelling, hypoxia and can generally cause a great deal of discomfort and ultimately limit the period of time that the contact lens can be worn.
In general, during contact lens wear, oxygen can reach the cornea either by diffusion through the lens material or by freshly oxygenated tear fluid being generated by the eye under the lens during lens motion as the lens is worn. However, some contact lenses may include components or formulations that are made of materials that have low oxygen permeability, and therefore most of the oxygen reaching the cornea is limited to oxygen from tear mixing.
Consequently, hydrogel lenses are usually preferred over other contact lens materials because they are more comfortable and allow for more oxygen to reach the eye. When a hydrogel lens is worn, some oxygen reaches the cornea directly by diffusion through the lens. The amount of oxygen delivered to the cornea through the lens is dependent on the oxygen permeability of the lens. There is also some natural generation of oxygenated tears by the eye which occurs under the lens, which further oxygenates the eye.
More recently, however, ophthalmic devices have been theorized to be capable of added functionality for which they may require nonpermeable or less permeable components and compositions to be incorporated. The inclusion of nonpermeable or less permeable components and compositions which make oxygen transmission and tear flow more difficult and, as a result, increase the risk of damage to the cornea.
Therefore, there is a need for an ophthalmic device composed of a hydrogel lens that is designed to provide greater oxygen transmissibility and increased tear flow to reduce the risk of damage to the cornea.